XenServer 6.5 is available in two commercial editions:
The Standard edition is our entry level commercial offering, with a range of features that will suit the needs of those customers who want a robust and high performing virtualization platform, but do not require the premium features offered by the Enterprise edition; while still wishing to benefit from the assurance of comprehensive Citrix Support and Maintenance.
The Enterprise edition is our premium offering, optimized for both server, desktop and cloud workloads. In addition to the Standard edition, it offers access to in-memory read caching, Dynamic Workload Balancing, GPU Virtualization (vGPU) with NVIDIA GRID, VMware vSphere to XenServer Conversion utilities, Intel Secure Measured Boot (TXT) and Export Resource Data.
Customers who have purchased XenApp or XenDesktop continue to have an entitlement to XenServer, which includes all the features contained within the Standard edition and many of those in the Enterprise edition, to include:
All hosts in a pool must be licensed. If you are running a XenServer pool with hosts that are licensed with different license types, the host with lowest license determines the features available to all members in the pool. Mixed pools of licensed and unlicensed hosts will behave as if all hosts were unlicensed. For information on managing licenses in XenServer 6.5, see Managing Licenses in XenServer 6.5.
XenCenter notifies you when your license is due to expire. You should purchase a license before it expires. When a XenServer license expires:
Citrix licensing has built-in timeout technology. After a startup license is checked out by a XenServer host, XenServer and the License Server exchange "heartbeat" messages every five minutes to indicate to each other that they are still up and running. If a XenServer host cannot contact the License Server, for example, due to problems with the License Server hardware or software or network failures, the server lapses into a 30-day licensing grace period. During the grace period, XenServer licenses itself through cached information and the hosts are allowed to continue operations as if they were still in communication with the License Server. The grace period is 30 days and when the grace period runs out, XenServer reverts to an unlicensed state. After communication is re-established between XenServer and the License Server, the grace period is reset.